Diplomacy looks to have a major focus in this title as you can create new satellite nations etc and then draw resources from them for having elevated someone to that throne. On top of that, the world is much larger and doesn’t only focus on Europe. From what we were able to sneak a peek at, the Colonies for all the major powers are included as is America, the Caribbean and India.
No one is always capable of winning every single battle, so in Napoleon’s Campaigns II, you can learn from your mistakes and losses. That means there is no reason to simply replay a battle solely because you lost. When you are defeated in battle it will open a specific opportunity. Risk is part of the game and in order to make great gains you will need to take a risk now and again.

Armies are not static and you can switch out units and leaders. However, even if you have a leader that is perfect for a specific place in your army, you might not be able to get him there without ruffling feathers of more senior officers which could cause you further problems. Of course, not all leaders are fit for all roles and so changes need to be made from time to time for the betterment of the cause. A battle could be won or lost based on the relationship between leaders of armies. One might need help and the other might simply drag his feet getting there and the battle will be lost.